Mechanism for steering tandem wheels of a tractor trailer assembly



Jan. 17, 1961 H c. r.- HUTCHENS 2,963,495

MECHANISM FOR STEERING TANDEM WHEELS OF A TRACTOR TRAILER ASSEMBLY Original Filed 001:. 21.

4 Sheets-Sheet 1 INVENTOR ATTORNEYS Jan. 17, 1961 C. MECHANISM FOR HUTCHENS 2,968,495

STEERING TANDEM WHEELS OF A TRACTOR TRAILER ASSEMBLY 7 Original Filed Oct. 21. 1955 4 Sheets-Sheet 2 INVENTOR CA /Mu: ffilrc/mvs ATTORNEYS- Jan. 17, 1961 c. T. HUTCHENS 2,968,495 MECHANISM FOR STEERING TANDEM WHEELS OF A TRACTOR TRAILER ASSEMBLY Original Filed Oct. 21 1955 4 Sheets-Sheet 5 1N VENT OR C'xmmz 3 7. //u TC/IEA/S ATTORNEYS CFZ bT. HUTCHENS Jan. 17, 1961 TANDEM WHEELS CTOR TRAILER ASSEMBLY 4 Sheets-Sheet 4 fill/Ill!!! I! llrllrllllzdr mm mm BY W f W ATTORNEYS l I I I I I I I l I l P NN AN 5 I -J "inl 00 3 F E \5 5 n u \F W IF m N9 \L Q H w h n: m m: u N: 2? mo. 0: l 2. 4'4 fl fi. 2

United States Patent MECHANISM FOR STEERING TANDEM WHEELS OF A TRACTOR TRAILER ASSEMBLY Charles T. Hutchens, P.0. Box 1355, Springfield, Mo.

Original application Oct. 21, 1955, Ser. No. 541,951,

now Patent No. 2,907,576, dated Oct. 6, 1959. Divided and this application May 18, 1959, Ser. No. 813,948 g 2 Claims. (Cl. 280-426) This invention relates to vehicles and more particularly to a semi-trailer construction.

In the conventional semi-trailer truck, the load on the trailer platform is carried at two points on the trailer; namely, the fifth wheel connection with the tractor and the rear axle thereof. Even if tandem axles are utilized, the weight is effectively carried at the front and rear only of the trailer. Consequently, in loading such trailer it often happens that the weight of the load is unequally distributed and when the trailer is checked at a weighing station, it is necessary to redistribute the load before the truck can pass inspection. Obviously, this gives rise to bothersome procedures which cut down on the efficiency ing platform, this problem can be substantially alleviated.

However, the placing of a load-bearing axle in the central portion of the platform gives rise to additional problems, such as more difficult steering and excessive stress to the trailer body due to variations in the road surface. To take care of these latter disadvantages, the present invention contemplates a novel means for steering a centrally disposed load-bearing axle.

Accordingly, it is an object of the present invention to provide a semi-trailer of the type described which includes a novel steering means for transmitting the horizontal angular movements of the tractor with respect to the trailer to the centrally disposed load-bearing axle so as to substantially overcome the steering dilficulties noted above.

Another object of the present invention is the provision of a novel steerable axle assembly disposed in the central portion of a semi-trailer and operable to prevent undue wear to the tires resulting from the steering of the tractor. I

These and other objects of the present invention will become more apparent during the course of the following detailed description and appended claims.

The invention may best be understood with reference to the accompanying drawings wherein an illustrative embodiment is shown.

In the drawings:

Figure 1 is a top plan view of a tractor-trailer unit or semi-trailer truck vehicle embodying the principles of the present invention and illustrating the manner in which the centrally disposed axle assembly is steered in response the tractor with l l Figure 4 is a side elevational view of the axle assembly; f Figure 5 is a cross sectional view taken along the line 5-5 of Figure 4; y Y

V Figure, 3 is a top plan view of one of the axlegassem- '4 Figure 6 is a fragmentary top plan view illustrating the king pin of the trailer which connects to the tractor fifth wheel;

Figure 7 is a vertical sectional view through the king pin; and

Figure 8 is an enlarged cross sectional view taken along the line 8-8 of Figure 2.

Referring now more particularly to the drawings, there is shown in Figures 1 and 2 a semi-trailer truck or tractor trailer unit which includes a conventional tractor, generally indicated at 10, and a trailer, generally indicated at 12. It will be understood that the tractor 10 may be of conventional construction and forms no part of the present invention except insofar as it is combined with the trailer 12 to form an operable unit.

The trailer 12 includes a body of conventional construction having a load-bearing platform, generally indicated at 14. This platform may be constructed in the conventional manner to include the usual structural beams, and the like, which are customarily utilized to form such platforms. Figure 7 illustrates certain of these beams, which are indicated at 16.

Mounted beneath the load-bearing platform 14 is a pair of axle assemblies, generally indicated at 18 and 20, the axle assembly 18 being disposed underneath the rear end of the platform and the axle assembly 20 being disposed underneath the central portion of the platform. Each of the axle assemblies is identical in construction, except as otherwise noted hereinafter, so that a description of. one should suflice to give a clear understanding of both. Q

As best shown in Figures 35, each axle assembly comprises a horizontal subframe 21 which may be constructed of a pair of transversely spaced, longitudinal tubular frame members 22, of angle iron construction or the like, and a pair of transverse, tubular frame members 24, of angle iron construction or the like, having their ends rigidly secured to the ends of the frame members 22, as by welding or the like. Extending downwardly and forwardly from the forward end of the subframe at each side thereof is an angular bracket 26, which preferably is of channel beam construction or the like, having its upper end rigidly secured to the forward end of the associated longitudinal frame member 22 by any suitable means, such as welding or the like. Preferably, a strap or brace 28, which may be of angle iron construction or the like, is rigidly secured between the lower end portion of each bracket 26 and the associated frame member 22 at a point spaced rearwardly from the forward end thereof; Each brace 28 is rigidly secured in position by any suitable means, such as welding or the like. Extending rearwardly from each bracket 26 is a link 30, preferably a tubular construction, having its forward end pivotally secured to the lower end of the bracket. The rear end of each link 30 is pivotally attached to a bracket 32, preferably made of transversely spaced plates, rigidly mounted on a saddle plate 33 secured to a axle housing 34. The axle housing 34 is arranged to carry a suitable axle 36 upon the ends of which are mounted suitable wheels 38 in a manner well known in the art.

A bracket 40, similar to bracket 32, is rigidly secured to central saddle plate 41 anchored to the central portion of the axle housing and extends upwardly and forwardly therefrom. The free end of the bracket 40 pivot-ally r'ec'eives the apex of a V-shaped or wish-bone link 42, preferably of tubular construction. The ends of the legs of the V-shaped link 42 are pivotally connected to the respective brackets 26 in vertically spaced relation to the pivots of the links 30 therewith. As best shown in Figure 4, it can be seen that the parallel links 30 and V:

j shaped link 42 constitute a parallel linkage mounting'for the axle housing which permits the latter to move vertically with substantially pure translatory motion.

This vertical movement of the axle housing is yieldably resisted by a load-bearing means, which} may take many forms, but, as shown, preferably comprises a pair of fiejxible, fluid-containing bellows 46, which may be constructed in any well-known manner. Thelower endof eachbellows 46 is connected to one side of the a le housing through a horizontal plate 48 rigidly securedthereto. Extending downwardly from each plate 48 is a pair of transversely spaced vertical plates 50, rigidly secured at their upper ends to the underside of the associatedplatefttl and having their lower edges rigidly secured to theupp'e'r surface of the saddle plates 33 and 41, respectively. To obtain additional strength, a transversely extending forward angle iron 52 may have its horizontal fiai g secured beneath the forward end of each plate 48- andits vertical flange secured to the forward ends of the vertical plates 50. Moreover, a rearward angle iron 54 maybe secured between the rear end of each plate 48 and associated plates 50 in a like manner.

Adjacent the rear end of one of the plates 48; a plate 55 is mounted for purpose hereinafter to be more fully described. To securely anchor this plate in position, an angular plate 56 is rigidly attached at its rear end to the rear end of the plate 55 and extends downwardly and forwardly therefrom so that its forward end portion may be rigidly secured to the loweredges of the vertical plates 50 extending rearwardly of the axle housing. Additional end plates 58 may be secured, as by welding and the like, between the lateral ends of angle iron 54; plate 55-a"nd angular plate 56-. It. will be understood that while" the above described construction is preferred; other. arrangements may be utilized, if desired. I

The upper end of each bellows 46- isrigidly secured beneath the subframe by means of a pair of spaced transverse frame members 60 rigidly secured at their ends to the longitudinal frame members 22 and extending across the. entire. subframe. Mounted beneath each end of the frame members 60 is a horizontal plate 62-which fixedly-receives the upper end of the associated bellows. If desired, chains 64 maybe secured between plates 48 and 62 to limit relative movement away from each other while shock bumpers 65 may be providedto limit-relative movement toward each other.

In order. to positively prevent lateral displac enen-t he'- twecnthe, axle'housing .34and subfranie 21,: a horizontal-1y disposed sway bar 66, or tubular construction, is con.- nected between the axle housing and subframe. As best shown in Figure 5, a bracket 68, preferably .made up'ofa pair of spaced plates, is rigidly secured 'to and extends downfrom one, side of the subframe. Between the lower end of the plates, one end of the sway bar 66' is pivotally attached and-the opposite end thereof is pivotally attached to a similar bracket 70, which is rigidly secured to and extends upwardly from the plate 55.

The axle assembly 18, constructed in the manner. in.- dicated above, is rigidly secured beneath the, rear end of the platform 14 by any suitable means, such as welding or the like. Thus, the axle housing of the assembly 18 may have yieldingly restricted vertical movement, but-the same is fixed so that no angular movement in a. horizontal plane is possible. The forw rd axle assembly 20', which 3,1150 Q$rueted in th manner. indicated above; is mounted beneath the central portion of the; platform for rotation about a vertical axis so as to enable the, same to be steered in accordance with the horizontal angular movement of the tractor with respect tothe. trailer. It will. be understood that any suitable means may beused to accomplish this movement as, for example, a-pivotpin haft'72 rigidly secured to the centralportionofthe I 21 and journaled within a suitable. bearing meander-m. As, best shown in Figures 1"and 2, it .prefenred that thepivotal axis ofthe forwardTaxle osbe spaced forwardly of the" rotary axis or the 7B wheels so that there will be a certain casteringeffect'which greatly aids in steering. It will be understood that the pivot pin 72 may be rigidly secured to the platform and journaled within the subframe, if desired.

In order to balance the load carried by each axle assembly and to prevent undue stress on the vehicle body due" to in the road, a load-equalizing system, generally indicated at 74, is provided which utilizes the bellows; ofgeach axle assembly. As best shown in Figtires 1 and 2, the bellows on the left hand side of the axle assemblies 18- and 29 are directly connected together by any suitable means, such as conduit 76. In like mannor, the bellows on the right hand side of the axle assemblies are directly interconnected by a second conduit 78. It is preferred that the interconnected bellows on each side of the trailer be filled with a suitable liquid, such as oil, water or the like, so that there will be substantially instantaneous response in one axle assembly to a variation in the pressure of the other. However, in order to cushion the effect of the non-compressible fluid utilized within the bellows, there is directly interconnected with each conduit 76 and 78 a pressure chamber 80 of conventional construction having a flexible diaphragm 81 therein (see Figure 8). Each pressure chamber is connected to its respective conduit so that one side of the flexible diaphragm communicates with the conduit and, hence, is adapted to contain the liquid therein. The opposite' side ofthe diaphragm preferably contains a compre'ssible' fluid, such as air or the like, and is directly conneared-wan asurge tank 82,- as by conduit 84 or the like. Itcan be seen that if the fluid pressure within the renews on either side of the trailer increases, this increas'linpressure' will be transmitted to the flexible" diaphragm and; due to the compressible fluid contained in the opposite side thereof, deflection of the diaphragm will be yieldingly resisted. Thus, the surge tanks act to limit the. amount the diaphragms can expand, which in turn limits the amount of relative vertical movement that an increase in pressure can cause. Stated differently, when the wheels of the trailer pass over a bump or the like, the shock of the bump is taken by the diaphragm which expands and transmits the shockto the air surge tank. This action effectively cushions all shocks encountered-andinsures an even travel of the platform.

If-desired, each ansurge tank 82 may be suitably connectle'd with the usual air brake tank 86 of the trailer, as by a conduit-88; Of course, suitable valves 90 should be provided forclosing ofi. communication between the air brake tank and the surge tank when the latter is in use.-

A' further feature made possible with the utilizationof the present load-equalizing system, is the provision of a gauge means for indicating the load carried by the axle assemblies. Preferably, suchmeans may simply take the form of a pair of conventional pressure-responsive gauges 92 separately connected with respective conduits 76- and 78' by any suitable means, such as conduits 94. The gauges 9 2may be located in any desirable position and, as' shown, they are disposed just forwardly of the rear axle assembly beneath the platform of thet'railer. It can be seen that since the bellows directly transmit the load of the platform to the axle housings, the fluid pressure contained within the bellows will be a. function of the load on theplatform. Thusit isa mere matter of calibrating the dial of the fluid pressurev gaugesto olita'in an indication of the load carried by the. Lanes.

As was indicated abovegthe forward axle assembly 20 is mounted for pivotal movement about the verticalshaft 72 so that the latter may be steered in accordance. with the horizontal angular movement of the tractor with re? spect tothe trailer. In order to effect this movement, there is provided a steering means, generally indicatedat 96. Asbest shown in Figures 6v and 7, theforwardiend of the platform 1 4 is provided with a vertically extending bearing 98' which is rigidlys'ecur'd to the adjacent beams 16 of the platform by means of suitable structural frame members, indicated at 100. These frame members may be rigidly secured to the beams 16 and to the bearing 98, as by welding or the like, sulficiently to firmly anchor the bearing in position. Rotatably mounted within the bearing 98, as by a bearing sleeve 102, is a king pin 104. The king pin extends downwardly from the bearing 98 and has its lower end arranged to engage within the fifth wheel of the tractor in the usual manner. In addition, a dog or lug 106 is rigidly secured to the lower end of the king pin and extends radially outwardly therefrom so as to fit within the king pin slot of the tractor fifth wheel. In this manner, the king pin 102 is fixedly received within the tractor fifth wheel or, at least, is connected therewith so as to move with the tractor angularly.

The upper end of the king pin 104 terminates in a square projection 108 which is received within a correspondingly shaped aperture 110 formed in one end of a radially extending arm 112. Arm 112 may be rigidly secured to the king pin by any suitable means such as bolts 113. Rigidly secured to the opposite end of arm 112 is an L-shaped bracket 114 having its horizontal leg disposed in parallel relation to the outer end of the arm 112. Pivotally secured between the horizontal leg of the bracket 114 and the outer end of the arm 112, as by pivot pin 116, is one end of a piston rod 118 forming a part of a fluid-operated ram unit, generally indicated at 120. The ram 120 further includes the usual piston (not shown) attached to the opposite end of the piston rod 118 which reciprocates within a conventional cylinder 122. The rear end of the cylinder 122 is pivotally mounted on the trailer platform by means of a U-shaped bracket 124 having a pivot pin 126 extending through the legs thereof and the end of the cylinder. Preferably, the ram 120 is double acting and includes conduits 128 and 130 connected to opposite ends thereof, which .con-

6 lateral stability, the mounting described above is preferred.

It can thus be seen that with the axle housing suspension utilized in the present axle assemblies, the assemlies may readily be located beneath the platform in the positions shown in the drawings, rather than both at the rear end as is customary. As was previously indicated, by disposing the forward axle assembly beneath the central portion of the trailer body, the load can be supported by the trailer more readily than is the case where only rear axles are provided. It is contemplated that the forward axle assembly may be so located as to support the trailer without the connection to the tractor fifth wheel. Of course, when the latter connection is made, a certain amount of the load will be assumed thereby, but this amount will be considerably less than would be the case if no centrally disposed axle were provided.

With the provision of a centrally disposed axle, turning is quite diflicul-t in that considerable lateral movement of the central axle housing will occur. This lateral movement results in excessive wear to the tires and it has been found that unless some means is provided for making the. central axle assembly track as the trailer is turned, this wear can be quite considerable. With the present invention a positive steering of the central axle assembly is accomplished by means of the steering system 134 in the manner indicated above. It will be understood that by appropriately varying the relative size of the ram units or by changing the effective lever arms through which the rams operate, varying proportions of duits are also connected in a like manner to the opposite ends of a cylinder 132 of a second ram unit, generally indicated at 134. The forward end of the cylinder 132 may be suitably pivoted to the platform, in a manner similar to the cylinder 122, and the ram further includes the usual piston (not shown) having a piston rod 136 extending therefrom. The outer end of the piston rod 136 is pivotally mounted to the subframe 21 of the forward axle assembly 20, at a position spaced radially from the pivot pin 72. It will be seen that since king pin 104 is fixed with respect to the tractor to move angularly therewith, horizontal angular movement of the tractor with respect to the trailer will cause a corresponding angular movement of the arm 112 with respect to the platform. This angular movement will result in an extension or retraction of the first ram 120 and because the latter is directly connected to the second ram 134, the latter will be extended or retracted a corresponding amount. Extension and retraction of the second ram 134 will cause the axle assembly 20 to pivot about pivot pin 72.

In operation, it will be seen that the suspension of each axle housing is such that yieldingly restricted vertical translational movement is permitted while torsional movement and lateral displacement are effectively prevented. Thus, the parallel links 30 and wish-bone link 42 serve to mount the axle housing for vertical translational movement, and in addition, prevent torsional movement thereof which may occur during braking and the like. Furthermore, the wish-bone link 42 provides a certain amount of lateral stability to the mounting, which lateral stability is completely insured by the provision of the horizontal sway bar 56. If desired, the pivotal connections of the sway bar and links may be resiliently journaled so as to substantially take up any lateral play that might occur, due to the connection of the sway bar, as the axle housing moves vertically with respect to the trailer platform. As stated above, the bellows 46 distribute the load from the platform to the axle housing and because the bellows do not afiord any the movement of the tractor can be transmitted to the central axle assembly; -As shown in Figure 1, it can be seen that the angularmovement of the tractor with re spect to'the trailer is somewhat greater than the angular movement of the axle assembly with respect to the trailer. This condition is desirable in that the portion of the trailer adjacent the central axle assembly does not swing or turn in as narrow an are as does the trailer. Moreover, by spacing the vertical pivot or steering axis of the central axle assembly forwardly of the axis of rotation of the wheels, steering is made easier in that the pull on the trailer aids in turning, on the same principle as castering wheel.

Another problem effectively solved by the present invention which arises as a result of mounting the forward axle assembly beneath the central portion of the trailer is that unevenness in the road can cause undue stress on the tractor body. For example, assuming that the trailer is being pulled over the crest of a bill, it will be seen that without equalized suspensions the central axle assembly would assume a large portion of the load while the fifth wheel and rear axle assembly would assome a rather minor portion of the load. Conversely, in passing through the bottom of a valley the fifth wheel and rear axle would assume the major load and the central axle would assume very little. This shifting of the load assumed by the various load bearing structures would soon cause undue stress in the body in addition to the excessive wear which would result in the fifth wheel and axle assemblies. With the present invention, the load carried by the forward axle assembly will at all times be equal to the load carried by the rear axle assembly. In the situations mentioned above, first, when the trailer is passing over the top of a hill, the bellows of the central axle assembly will be compressed due to the increased load thereon and the depression of the bellows will be transmitted to the bellows of the rear axle assembly, thus extending the same. Likewise in passing a dip or valley in the road, the pressure on the rear axle assembly will be increased and the bellows depressed, but such increase in pressure and depression will be directly transmitted to the forward axle assembly to extend the same. In this manner, not only is undue stress eliminated, but even travel of the platform is insured.

Furthermore, the present load-equalizing system provides an, efficient means for cushioning shocks that might occur .When the wheels run over an object or enter a depression. In this case, the rapid increase or decrease of the pressure within the associated bellows will result in deflection of the diaphragm of the pressure chamber. Since the deflection of the diaphragm is yieldably resisted by the air contained within the surge tank, such shocks are effectively cushioned and the trailer is kept on a near even keel. This latter condition is true in going around a curve, a condition which is virtually impossible to accomplish with conventional leaf-spring suspension systems. Finally, the present load-equalizing system enables the simple provision of gauge means for indicating the load carried by the axle assembly at all times with the obvious advantage attendant thereto.

It thus will be seen that the objects of this invention have been fully and effectively accomplished. It will be realized,- however, that the foregoing specific em bodiment has been shown and described only for the purpose of illustrating the principles of this inventtion and is subject to extensive change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.

This application is a divisional of my pending application Serial No. 541,951, filed October 21, 1955, now United States Patent No. 2,907,576.

I claim:

1-. In a trailer for use with a tractor having a fifth Wheel, a load bearing platform, a rear axle assembly fixedly secured-to'the rear endof said platform,;a,steerable: axle assembly mounted beneathsaid platform: intermediate the front and rear endsthereof, a king pin pivotally mounted on the front end of said platform for fixedlyengaging the tractor fifth Wheel, and means connected between said steerable axle assembly and said king pin for transmitting the pivotal movement of the latter occasioned by relative horizontal angular movement between said platform and the tractor to said steerable axle assembly so that the latter will move angularly in accordance with the relative angular movement be tween said platform and the tractor, said last-mentioned means comprising an arm on said king pin, a first double acting fluid ram operatively connected between said arm and said platform, a second double acting fluid ram operatively connected between said steerable axle assembly and said platform, and closed conduit means interconnecting said first and second rams, said closed conduit means including a first conduit connected to one end of one of said double acting fluid rams and .to one end of the other fluid ram and a second conduit connected to the other end of one fluid ram and the other end of the other fluid ram.

2. In a trailer as defined in claim 1, said king pin having a transversely extending dog on the lower end thereof for engaging the tractor fifth wheel to prevent rotation of said king pin with respect to the tractor.

References Cited inthe file ofthis patent UNITED STATES PATENTS 2,131,760 Schaefer Oct. 4, 19.38 2,152,511 Vanderwerf Mar. 28, 1939 2,167,943' Fox Aug; 1, 1939 2,433,269 Fellaba-um Dec; 23, 1947 2,717,787 Ward. Sept; 13, 19.55 2,797,106 Lorr June25, 1957 g FOREIGN PATENTS 948,629 France Jan. 31, 1949 

